1. Field
Example embodiments relate to field effect semiconductor devices including a gallium nitride (GaN)-based semiconductor having a gate electrode formed on a surface opposite to a surface for forming a source and a drain, and methods of manufacturing the same.
2. Description of the Related Art
Due to the ongoing development of communication technologies, research is being conducted on communication devices for use in high frequency bands. In particular, field effect semiconductor devices (e.g., high electron mobility transistors (HEMTs)) are receiving considerable attention as communication devices for use in high frequency bands.
A HEMT is a heterogeneous junction field effect transistor including a structure formed by combining materials having different band gaps. Because a heterogeneous junction structure is formed of materials having different band gaps, the electron mobility may be increased by creating a two-dimensional electron gas (2D-EG) region in a junction interface.
Normally, because silicon (Si) used to form a semiconductor device has low electron mobility, a substantially high source resistance may be generated. Thus, research is being conducted on various ways to use Groups III through V semiconductor compounds to form high electron mobility transistors. In particular, a gallium nitride (GaN)-based compound has a relatively wide band gap and high electron saturation velocity, and is chemically stable. As such, gallium nitride-based compounds are receiving considerable attention as a material for forming high electron mobility transistors. Active research is being conducted on high electron mobility transistors formed of GaN-based compounds as high-temperature, high-output and high-frequency electronic devices.
Generally, a high electron mobility transistor has normally-on characteristics. As such, excessive currents may flow when power is supplied to devices including high electron mobility transistors, and a negative power supply is required to change the high electron mobility transistor to an off-state. One of the GaN-based compound layers may be formed substantially thin in order to obtain normally-off characteristics of the transistor, thereby preventing normally-on characteristics. However, an electric field may be weakened due to piezo-polarization, and the concentration of electrons of a 2D-EG region formed in the heterogeneous junction may be reduced.